"The body of an adult male contains about five litres of blood, that of a woman or a child less."

5 L

New Book of Popular Science. Connecticut: Grolier, 1996: 197.

"In just a single day, the heart pumps the body's supply of blood-approx. 5 quarts (4.7 liters) in an average adult …."

4.7 L

In humans, blood is the fluid that transports nutrients and
oxygen to every cell in the body. It also transports wastes away
from cells. Blood keeps our body temperature steady by carrying
excess heat from regions of the body to the skin where it can
be dissipated. It also fights infection and carries chemicals
that regulate many body functions.

Blood is composed of a yellowish fluid, called plasma, in which
are suspended the millions of cells that constitute 45% by volume
of whole blood. A cubic millimeter of human blood contains about
5 million red blood cells, or erythrocytes; 5,000 to 10,000 white
blood cells or leukocytes; and 200,000 to 300,000 platelets or
thrombocytes. The blood also carries many salts and organic substances
in solution in the blood plasma.

In an average healthy adult, the volume of blood is about one-eleventh
of the body weight. Most sources state the volume of blood in
an average human adult, who is between 150 to 160 pounds, as between
4.7 and 5 liters, although the more recent sources state the volume
of blood in an average adult as 4.7 liters. Sources state that
an 80-pound child had about half that amount, and an 8-pound infant
has about 8.5 ounces. People who live at high altitudes, where
the air contains less oxygen, may have up to 1.9 liters more blood
than people who live in low altitude regions. The extra blood
delivers additional oxygen to body cells. The heart pumps all
the blood in the body each minute when the body is at rest.

According to a source from 1973, the volume of blood can be
measured one of two ways. Each depends upon putting a known quantity
of some substance in the body, and, after it has been distributed
uniformly in the whole circulating fluid, measuring the degree
of dilution which has taken place. The substances most commonly
used then were carbon monoxide, Evans blue dye, and radioactive
chromium.